Upgrade to remove ads
PHARM Week 2 Study Tips-Chapter 43
Terms in this set (61)
The circulatory system has two primary functions:
(1) to deliver oxygen, nutrients, hormones, electrolytes, and other essentials to cells; and (2) to remove carbon dioxide, metabolic wastes, and other detritus from cells.
The system has two major divisions:
the pulmonary circulation and the systemic circulation
The pulmonary circulation delivers blood to the
The systemic circulation delivers blood to
all other tissues.
The circulatory system is composed of the
heart and blood vessels
transport blood under high pressure to tissues.
serve as control valves to regulate local blood flow.
are the sites for exchange of fluid, oxygen, carbon dioxide, nutrients, hormones, wastes, and so forth
collect blood from the capillaries.
transport blood back to the heart and serve as a major reservoir for blood.
large increases in arterial pressure (AP) cause only
small increases in arterial diameter
small increases in venous pressure cause
large increases in venous diameter.
The adult circulatory system contains 5 L of blood how is it distributed?
9% is in the pulmonary circulation, 7% is in the heart, and 84% is in the systemic circulation
Blood moves within vessels because the force that drives flow is
greater than the resistance to flow.
Resistance to flow is determined by
the diameter and length of the vessel and by the blood's viscosity
when vessels dilate, resistance declines, causing blood ; when vessels constrict, resistance rises, causing blood
flow to increase; flow to decline
Three mechanisms help ensure that blood returns to the heart:
(1) negative pressure in the right atrium helps "suck" blood toward the heart; (2) constriction of smooth muscle in the venous walls increases venous pressure, which drives blood toward the heart; and (3) most important, the combination of venous valves and skeletal muscle contraction constitutes an auxiliary "venous pump."
In the average adult, cardiac output is
about 5 L/min
every minute the heart pumps the equivalent of
all the blood in the body.
Cardiac output (CO) =
Heart rate × Stroke volume
For the average individual, the heart rate is about 70 beats per minute and the stroke volume is about
70 mL; therefore, the average CO is 4.9 L/min (70 × 70)
The rate is increased by
the sympathetic branch acting through beta1-adrenergic receptors in the sinoatrial (SA) node
The rate is decreased by
the parasympathetic branch acting through muscarinic receptors in the SA node
The stroke volume is determined largely by three factors:
(1) myocardial contractility, (2) cardiac afterload, and (3) cardiac preload
Myocardial contractility is defined as
the force with which the ventricles contract
Preload is defined formally as
the amount of tension (stretch) applied to a muscle before contraction
stretch is determined by the ventricular filling pressure, or the______ ; the greater the filling pressure, the more the ventricles stretch.
force of venous return
Afterload is defined as
the load against which a muscle exerts its force.
For the heart, afterload is
the arterial pressure that the left ventricle must overcome to eject blood.
Cardiac afterload is determined primarily by
peripheral resistance, which in turn is determined by constriction and dilation of arterioles
Starling's law states
that the force of ventricular contraction is proportional to the length of muscle fibers. Therefore, when more blood enters the heart, more is pumped out. As a result, the healthy heart is able to precisely match output with venous return.
From the perspective of pharmacology, the most important determinant of venous return
is the systemic filling pressure
Because the myocardium operates under___ , the right and left ventricles in a healthy heart always pump____ .
Starling's law; exactly the same amount of blood
In a failing heart, Starling's law breaks down; that is, the force of contraction
no longer increases in proportion to increased ventricular filling. As a result, blood backs up behind the failing ventricle.
Arterial pressure =
Peripheral resistance × Cardiac output
Peripheral resistance is regulated primarily through
constriction and dilation of arterioles.
Under normal circumstances, the arterial pressure is regulated primarily by three systems:
the autonomic nervous system (ANS), the renin-angiotensin-aldosterone system (RAAS), and the kidneys
The ANS acts in two ways:
(1) it responds rapidly (in seconds or minutes) to acute changes in blood pressure, and (2) it provides steady-state control
The___ responds more slowly, taking hours or days to influence the AP
kidneys, which are responsible for.
long-term control, may take days or weeks to adjust the AP
The ANS regulates the AP by adjusting the
CO and peripheral resistance. Sympathetic tone to the heart increases the heart rate and contractility, thereby increasing the CO
parasympathetic tone slows the heart, thereby
reducing the CO
The baroreceptor reflex maintains the AP at a
When the AP changes, the reflex immediately
attempts to restore it to the preset value.
The reflex works as follows:
Baroreceptors in the aortic arch and carotid sinus sense the AP and relay this information to the vasoconstrictor center of the medulla. When the AP changes, the vasoconstrictor center compensates by sending appropriate instructions to the arterioles, veins, and heart
The baroreceptor reflex is poised for
rapid action but not for sustained action
When the AP remains elevated or lowered, the system resets to the new pressure within___ . After this, the system perceives the new (elevated or reduced) pressure as ___and stops responding
1 to 2 days; "normal"
Drugs that lower the AP trigger the
The RAAS supports the AP by causing
(1) constriction of arterioles and veins and (2) retention of water by the kidneys
Vasoconstriction is mediated by____ ; water retention is mediated in part by ____
When the AP remains low for a long time, the kidney responds by
retaining water, which in turn causes the AP to rise
Postural hypotension, also known as orthostatic hypotension, is a
reduction in the AP that can occur when a person moves from a supine or seated position to an upright position.
The cause of hypotension is
pooling of blood in the veins, which reduces venous return, which in turn reduces the CO
When postural hypotension occurs, the baroreceptor reflex can restore the AP by
(1) constricting veins and arterioles and (2) increasing the heart rate. In patients taking drugs that interfere with venoconstriction, postural hypotension is more intense and more prolonged
_____ protect the cardiovascular system in the event of volume overload, a condition that increases preload and thereby increases the CO and AP
Natriuretic peptides work primarily by
(1) reducing blood volume and (2) promoting the dilation of arterioles and veins
The family of natriuretic peptides has three principal members:
atrial natriuretic peptide (ANP), B- (brain) natriuretic peptide (BNP), and C-natriuretic peptide (CNP)
ANP is produced by
myocytes of the atria
BNP is produced by
myocytes of the ventricles (and, to a lesser extent, by cells in the brain, where BNP was discovered)
CNP is produced by
cells of the vascular endothelium
ANP and BNP have similar actions, both peptides
reduce blood volume and increase venous capacitance, thereby reducing cardiac preload
YOU MIGHT ALSO LIKE...
Ch. 43 Review of hemodynamics
UWEC NRSG 245 Pharmacology | Exam 3 (Ch. 43)
OTHER SETS BY THIS CREATOR
Skills: Week 1
Skills- Final Review
Skills- Week 3
Skills: Week 2